WO2011148955A1

WO2011148955A1 - Drying furnace and drying method

Info

Publication number: WO2011148955A1
Application number: PCT/JP2011/061911
Authority: WO
Inventors: 航佐藤
Original assignee: 本田技研工業株式会社
Priority date: 2010-05-26
Filing date: 2011-05-24
Publication date: 2011-12-01
Also published as: JP2011245412A; CN102906521B; JP5568377B2; CN102906521A; US8997374B2; US20130061489A1

Abstract

Disclosed is a drying furnace (20) which dries a subject to be dried (11) using hot air. In the drying furnace, subject (11) areas (35, 42), which have heat capacity larger than that of other areas (37, 44) and are not easily heated, are provided with heaters (36, 38, 43, 45), which heat the areas (35, 42) by applying radiation heat so that the temperature of the areas is close to the temperature of other areas (37, 44).

Description

Drying furnace and drying method

The present invention relates to a drying technique for drying an object to be dried with hot air.

One type of drying oven is a hot air circulation drying oven. In this drying furnace, the material to be dried is dried by circulating hot air. In many cases, an object to be dried is a combination of a plurality of members, and there are thick portions and thin portions. The thick part has a large heat capacity, so it is difficult to warm up. On the other hand, the thin-walled portion is a portion that is easily warmed because of its small heat capacity. When such an object to be dried is dried in a hot air circulation type drying oven, the drying is continued until the drying of the part that is difficult to warm is completed, even though the drying of the part that is easy to warm is completed. Becomes longer. For this reason, a technique for improving the temperature rising rate of a portion that is difficult to warm is required.

Conventionally, as a technique for improving the rate of temperature increase in a portion of the object to be dried that is difficult to warm, various drying techniques for heating a part of the object to be dried in addition to heating with hot air have been proposed (for example, Patent Document 1 (FIG. 4). )reference.).

Patent Document 1 will be described with reference to FIG.
As shown in FIG. 11, the drying furnace 100 is provided with a furnace body 102 formed so as to surround an object to be dried 101, and a hot air provided in the lower part of the left wall 103 and the lower part of the right wall 104 of the furnace body 102. A pair of

hot air inlets

105 and 106 to be inserted, and a pair of

hot air outlets

109 and 111 provided in the

lower headers

107 and 108 connected to the

hot air inlets

105 and 106 to eject the hot air taken in the furnace body 102; , Connected to a pair of

hot air inlets

114 and 115 respectively provided in

upper headers

112 and 113 provided on the upper inner side of the left wall 103 and the upper inner side of the right wall 104 and sucking hot air in the furnace body 102, and the

upper headers

112 and 113, respectively. And a pair of

hot air outlets

116 and 117 for taking hot air out of the furnace body 102.

A blower is connected to the

hot air outlets

116 and 117, a heating device is connected to the discharge side of the blower, and

hot air inlets

105 and 106 are connected to the heating device. In addition, a pair of left and

right heaters

118 and 119 are disposed in the vicinity of the lower portion of the object to be dried 101. These

heaters

118 and 119 are connected to a blower and a heating device.

In the drying furnace 100, the hot air blown out from the

hot air outlets

109 and 111 is brought into contact with the material to be dried 101 to dry the material to be dried 101. Hot air is discharged from the inside of the furnace body 102 through the

hot air inlets

114 and 115 to the outside of the furnace body 102, heated, and ejected from the

hot air outlets

109 and 111 again through the hot

air intake ports

105 and 106. That is, the to-be-dried object 101 is dried by the circulating hot air.

In addition, if the bottom 121 of the object to be dried 101 is thick, the bottom 121 has a large heat capacity and is difficult to warm up. Hot air is ejected from the ejection nozzles 122 of the

heaters

118 and 119 toward the bottom 121 of the object to be dried 101. By this hot air injection, the rate of temperature rise at the bottom 121 of the object to be dried 101 can be improved.

However, in the drying furnace 100, the hot air ejected from the ejection nozzles 122 of the

heaters

118 and 119 diffuses around the bottom 121 of the object to be dried 101, so that it is difficult to give a targeted amount of heat to the targeted portion. . If the drying time is lengthened as a measure, the temperature of the bottom 121, which is a part that is difficult to warm up, rises, but the part that is easy to warm of the article 101 receives extra heat even though the temperature has already been raised. become. This is not preferable from the viewpoint of energy saving.

Japanese Unexamined Patent Publication No. 2000-197845

Embodiment of this invention provides the drying technique which can reduce the excess calorie | heat amount provided with respect to the site | part which is easy to warm in to-be-dried material.

According to the embodiment of the present invention, the drying furnace 20 that dries the object to be dried 11 with hot air radiates heat to the

parts

35 and 42 that have a larger heat capacity than the

other parts

37 and 44 and are difficult to warm in the object to be dried 11. In addition,

heaters

36, 38, 43, 45 may be provided that heat the

portions

35, 42 that are difficult to warm up so as to approximate the temperatures of the

other portions

37, 44.

In addition, according to the embodiment of the present invention, the drying method of drying the object to be dried 11 with hot air using the drying furnace 20 includes a temperature raising step for increasing the temperature of the object to be dried 11 and a heat capacity in the object to be dried. The temperature of the

parts

35 and 42 that are larger than the

other parts

37 and 44 and difficult to warm is measured by the first

temperature measuring parts

73 and 77, and the temperature of the

other parts

37 and 44 is measured by the second

temperature measuring parts

75 and 79. A temperature measuring step, a local heating step of heating the

portions

35 and 42, which are difficult to warm by applying radiant heat to the

portions

35, 42 which are difficult to warm, to approximate the temperatures of the

other portions

37, 44; And a temperature holding step for keeping the temperature of 11 constant.

Other features and effects will be apparent from the description of the embodiments and the appended claims.

FIG. 1 (a) to FIG. 1 (d) are diagrams illustrating a mechanism for drying a paint on the surface of an object to be dried according to a typical embodiment. FIG. 2A and FIG. 2B are graphs for explaining the local heating start timings of the comparative example and the example. FIG. 3A and FIG. 3B are graphs for explaining the heating rate of the comparative example and the example. It is sectional drawing of a drying furnace. FIG. 5 is an enlarged view of part 5 of FIG. 4. FIG. 6 is a sectional view taken along line 6-6 of FIG. FIG. 7 is a sectional view taken along line 7-7 in FIG. FIG. 8 is a sectional view taken along line 8-8 in FIG. FIG. 9A to FIG. 9C are diagrams for explaining the operation of the temperature measuring section and the heater. It is a flowchart of a drying method. It is a figure explaining the basic composition of the conventional technology.

According to the embodiment of the present invention, the drying furnace has a heat capacity larger than that of other parts in the object to be dried, and the temperature of the part that is difficult to warm by applying radiant heat approximates the temperature of the other part. Equipped with a heater to heat. Here, the other part may be a part that is easily warmed. In the drying furnace, a portion that is difficult to warm in the object to be dried is locally heated with a heater while the entire object to be dried is heated with hot air. Since the radiant heat generated by the heater is absorbed by the object to be dried in the form of electromagnetic waves, it is possible to reliably heat the portion of the object to be dried that is difficult to warm. This heating raises the temperature of the part that is difficult to warm in the object to be dried, so that the temperature of the part that is difficult to warm can be reliably approximated to the temperature of the part that is easily warmed.

Temporarily, if a part that is difficult to warm in the dried object is heated locally with hot air blown from the injection nozzle while the whole object to be dried is heated with hot air, the sprayed hot air diffuses around the part that is difficult to warm. . Due to the diffusion of the hot air, the hot air does not reach the part that is difficult to warm in the material to be dried, and the part that is difficult to warm cannot easily be heated. In order to raise the temperature of the portion that is difficult to warm, it is sufficient to continue heating, but the portion that is likely to be warmed has already been heated, and therefore receives extra heat.

In that respect, in the drying furnace of the embodiment, by applying radiant heat to a part that is difficult to warm in the object to be dried, the temperature of the part that is difficult to warm can be reliably approximated to the temperature of the part that is easily warmed. That is, since it is possible to raise the temperature of the part that is difficult to warm in the object to be dried and the part that is easy to warm up, it is not necessary to apply extra heat to the part that is easily warmed. Therefore, it is possible to provide a drying furnace that can reduce the amount of heat that has been given to a portion that is easily warmed in an object to be dried.

The heater may be a near infrared lamp. As infrared rays, near infrared rays and far infrared rays having wavelengths longer than the near infrared rays are known. It is also known that the absorption rate (energy absorption rate) varies depending on the type of irradiation target. When the object to be dried is a vehicle body, the object to be dried is composed of an iron-based material constituting the vehicle body and a coating film formed by applying an acrylic water-based paint or the like to the vehicle body. Table 1 below shows the absorptance of iron and acrylic water-based paints.

If the coating film is mainly heated, far-infrared rays having an absorptance of 74% in the acrylic water-based paint are suitable. However, the coating applied to the inner surface of the vehicle body is not effective. Therefore, in the embodiment, near infrared light having an absorption rate of 35% is adopted for iron, iron, that is, the vehicle body is mainly heated, and the coating film on the inner surface is dried by the heat of the vehicle body. By using near-infrared rays, it is possible to raise the temperature of an object to be dried in a time-consuming manner by utilizing the heat conduction of a member even for a portion that is not directly irradiated with near-infrared rays.

The drying furnace may include a first temperature measuring unit that measures the temperature of a part that is difficult to warm up and a second temperature measuring unit that measures the temperature of another part upstream of the heater. Further, the drying furnace may include a control unit that controls the output of the heater based on temperature information of the first temperature measuring unit and the second temperature measuring unit. When the temperature of the part that is difficult to warm measured by the first temperature measuring unit has a large difference from the temperature of the other part measured by the second temperature measuring unit, a high output command is sent from the control unit to the heater . On the other hand, if the temperature of the part that is difficult to warm measured by the first temperature measuring unit has a small difference from the temperature of the other part measured by the second temperature measuring unit, the controller outputs a low output command to the heater. Send. In this way, the temperature of the part of the object to be dried that is difficult to warm is compared with the temperature of the other part, and the heater is controlled by the control unit so as to output an appropriate amount of heat according to the temperature difference. Therefore, an appropriate amount of heat can be given to the portion of the object to be dried that is difficult to warm from the heater.

In addition, according to the embodiment, the drying method is performed using a drying furnace that dries an object to be dried with hot air. In addition, the drying method includes a temperature raising step for increasing the temperature of the object to be dried, and a temperature of a part of the object to be dried that has a heat capacity larger than that of other parts and is not easily warmed by the first temperature measuring unit. A temperature measurement step of measuring the temperature of the part with the second temperature measuring unit, and heating the radiant heat to a part that is difficult to warm in the object to be dried so that the temperature of the part that is difficult to warm approximates the temperature of the other part. You may consist of a local heating process and the temperature holding process which hold | maintains the temperature of to-be-dried material uniformly. Here, the other part may be a part that is easily warmed.

Since the radiant heat used in the local heating process is absorbed by the object to be dried in the form of electromagnetic waves, it is possible to reliably heat the portion of the object to be dried that is difficult to warm. This heating raises the temperature of the part that is difficult to warm in the object to be dried, so that the temperature of the part that is difficult to warm can be reliably approximated to the temperature of the part that is easily warmed.

In that respect, in the drying method of the embodiment, in the local heating step, by applying radiant heat to the part that is difficult to warm in the object to be dried, the temperature of the part that is difficult to warm can be reliably approximated to the temperature of the part that is easily warmed. . That is, since it is possible to raise the temperature of the part that is difficult to warm in the object to be dried and the part that is easy to warm up, it is not necessary to apply extra heat to the part that is easily warmed. Therefore, it is possible to provide a drying method capable of reducing the excess amount of heat given to a portion that is easily warmed in an object to be dried.

The object to be dried may be one that has been coated before being put into the drying furnace. In addition, when the radiant heat is applied to the part of the object to be dried that is difficult to warm in the local heating step, the temperature of the part that is difficult to warm measured by the first temperature measuring unit is equal to the crosslinking temperature of the paint applied to the object to be dried. It may be the time when it is reached. Below, the drying mechanism of the paint on the surface of the material to be dried will be described.

When the mist-like paint is sprayed on the material to be dried, the paint particles are directed toward the surface of the material to be dried. At this time, the surface temperature of the material to be dried is room temperature.
When the paint particles collide with the surface of the object to be dried, the paint adhering to the surface of the object to be dried swells. At the same time, the volatile components of the paint evaporate and the paint hardens in a wavy state.
Next, when the object to be dried that has been coated is placed in a drying furnace, the paint solidified on the surface of the object to be dried is heated by hot air. The heated paint fluidizes. Also, surface tension and gravity act on the paint in the amplitude direction of the swell. Thereafter, a smooth coating film is formed.
When the temperature of the object to be dried further rises and the surface temperature of the object to be dried reaches the crosslinking temperature of the paint, radiant heat is applied to the surface of the object to be dried. Since the crosslinking has already started at this point, the paint does not flow and the smooth coating film formed above can be maintained. As a result, a smooth coating film can be obtained.

Temporarily, if the object to be dried is put in a drying furnace and radiant heat is applied to a portion that is difficult to warm in the object to be dried simultaneously with the start of hot air drying, the paint applied to the object to be dried is fluidized. However, by locally heating the object to be dried with radiant heat, the temperature rise rate of the object to be dried increases, so that the paint becomes hot and the paint hardens while the flow is insufficient. Therefore, it becomes difficult for the coating film to become smooth, and the quality of the coating film decreases.

In that respect, in the drying method of the embodiment, when the temperature of the portion that is difficult to warm in the material to be dried reaches the crosslinking temperature of the paint applied to the material to be dried, radiant heat is applied to the portion that is difficult to warm in the material to be dried. Add That is, local heating by radiant heat is performed on a portion of the object to be dried that is difficult to warm when a certain time has elapsed since the start of hot air drying. Between the start of hot air drying and the start of local heating, the paint applied to the region that is difficult to warm up fluidizes. At the start of hot air drying, the temperature rise rate of the material to be dried is small, so that the paint flows sufficiently and then becomes hot and solidifies. Therefore, since a smooth coating film can be obtained, the quality of the coating film is improved.

The heat source of radiant heat may be near infrared. In this case, as shown in Table 1 above, iron, that is, the vehicle body is mainly heated by the near infrared ray having an absorption factor of 35% in iron, and the coating film on the inner surface can be dried by the heat of the vehicle body. As a result, by using near-infrared rays, it is possible to raise the temperature of the object to be dried without requiring time by utilizing the heat conduction of the member even for a portion that is not directly irradiated with near-infrared rays.

<Example>
Examples will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals. In the embodiment, the object to be dried is a vehicle body. Moreover, a side sill is illustrated as a site | part whose heat capacity is larger than another site | part, and is hard to warm, and a door outer panel is illustrated as another site | part. Moreover, in the Example, the vehicle body which enters a drying furnace is painted by the coating equipment provided in the upstream of a drying furnace.

As shown in FIG. 1A, when a mist-like paint is sprayed onto the vehicle body 11 (described later in detail), the paint particles 12 are directed toward the surface 13 of the vehicle body 11 as indicated by an arrow (1). At this time, the surface temperature of the vehicle body 11 is normal temperature.

When the paint particles 12 collide with the surface 13 of the vehicle body 11, the paint 14 attached to the surface 13 of the vehicle body 11 swells as shown in FIG. At the same time, since the volatile components of the paint 14 evaporate, the paint 14 hardens in a wavy state.

Next, when the painted vehicle body 11 is put into a drying furnace (details will be described later), the paint 14 solidified on the surface 13 of the vehicle body 11 is heated by hot air. The heated paint 14 is fluidized. Further, surface tension and gravity act on the paint 14 in the amplitude direction of the swell. Thereafter, as shown in FIG. 1C, a smooth coating film 15 is formed.

When the temperature of the vehicle body 11 further rises and the surface temperature of the vehicle body 11 reaches the crosslinking temperature of the paint, radiant heat from a heater (described later in detail) is applied to the surface 13 of the vehicle body 11. Since the crosslinking has already started at this point, the paint does not flow, and the smooth coating film 15 formed in FIG. 1C can be maintained. As a result, as shown in FIG. 1D, a smooth coating film 15 can be obtained.

Next, the start time of local heating will be described. A comparative example will be described with reference to FIG. 2A, and an embodiment will be described with reference to FIG. As shown in FIG. 2A, simultaneously with the start of hot air drying, when a side sill (detailed later) of the vehicle body is locally heated with radiant heat in addition to Ta hot air for a certain time (detailed later), a temperature rise curve is obtained. In this curve, the heating rate increases at the start of heating. Further, the surface temperature of the vehicle body reaches the temperature tc during the local heating time Ta. This temperature tc coincides with the crosslinking temperature of the paint.

If the local heating to the side sill of the vehicle body is started simultaneously with the start of hot air drying, the paint applied to the side sill is fluidized. However, since the heating rate of the vehicle body increases due to local heating, the paint becomes hot and the paint hardens while the flow is insufficient. Therefore, it becomes difficult for the coating film to become smooth, and the quality of the coating film decreases.

As shown in FIG. 2B, when the time T has elapsed from the start of hot air drying, the side sill of the vehicle body is locally heated with radiant heat in addition to Ta hot air for a certain period of time. As a result, a temperature rise curve is obtained. In this curve, the rate of temperature increase at the start of heating is smaller than that in FIG. Further, in FIG. 2B, at the local heating start time T, the surface temperature of the vehicle body reaches the temperature tc. This temperature tc coincides with the crosslinking temperature of the paint.

The local heating of the side sill of the car body is performed when time T has elapsed from the start of hot air drying. Between the start of hot air drying and the start of local heating, the paint applied to the side sill is fluidized. Since the heating rate of the vehicle body is small at the start of hot air drying, the paint flows sufficiently and then becomes hot and hardens. Therefore, since a smooth coating film can be obtained, the quality of the coating film is improved.

Next, the relationship between local heating and drying time will be explained. A comparative example will be described with reference to FIG. 3A, and an embodiment will be described with reference to FIG. When the painted vehicle body is placed in a drying furnace in which hot air is circulating and dried, the target surface temperature of the vehicle body is maintained at 160 ° C. for a target time Th = 11 minutes, as shown in FIG. For example, it took 41 minutes in total.

On the other hand, as shown in FIG. 3B, the car body that has been coated in the drying furnace is dried with hot air, and when 20 minutes have elapsed from the start of hot air drying, Ta = 1. The side sill of the car body is locally heated with radiant heat from the heater for a minute.

This local heating increases the rate of temperature increase of the side sill, so that the temperature increase curve of the side sill approaches the temperature increase curve of the door outer panel (described later in detail) of the vehicle body. As a result, it took a total of 32 minutes, for example, to maintain the target surface temperature 160 ° C. of the side sill for the target time Th = 11 minutes. When FIG. 3A is compared with FIG. 3B, the time of Td = 9 minutes can be reduced compared to FIG. 3A by using the heating rate of FIG. 3B. . A drying furnace for carrying out such drying of the vehicle body will be described with reference to FIG.

As shown in FIG. 4, the drying furnace 20 has a furnace body 22 that surrounds the plurality of vehicle bodies 11 being conveyed by a conveyor 21. In the furnace body 22, the paint applied to the vehicle body 11 is dried with hot air. After the hot air is introduced into the furnace body 22, it contacts the vehicle body 11 and is taken out of the furnace body 22. The hot air taken out from the furnace body 22 is heated and introduced into the furnace body 22 again. That is, the drying furnace 20 is a hot air circulation type drying furnace.

The drying furnace 20 includes a first hot air heating unit 23 disposed on the upstream side and a second hot air heating unit 24 disposed on the downstream side. The first hot air heating unit 23 corresponds to a temperature raising unit that raises the temperature of the vehicle body 11. The second hot air heating unit 24 corresponds to a holding unit that holds the temperature of the vehicle body 11 that has been heated.
In addition, a local heating unit 25 (described later in detail) is provided at the end of the first hot air heating unit 23. Next, the configuration of the local heating unit 25 will be described.

As shown in FIG. 5, the local heating unit 25 is provided with a local heating device 26 (described later in detail) for heating the local part of the vehicle body 11. An upstream temperature measuring unit 27 is provided upstream of the local heating unit 25, and an upstream temperature measuring device 28 (details will be described later) for measuring the temperature of each part of the vehicle body 11 is provided in the upstream temperature measuring unit 27. ing. Further, a downstream temperature measuring unit 29 is provided downstream of the local heating unit 25, and a downstream temperature measuring device 31 (described later in detail) that measures the temperature of each part of the vehicle body 11 is provided in the downstream temperature measuring unit 29. Is provided. Next, the detailed structure of the local heating device 26 will be described with reference to FIG.

As shown in FIG. 6, the local heating device 26 is supported by a portal frame 32 erected in the furnace body 22. The local heating device 26 is provided on the left pillar 33 of the portal frame 32, and includes a left inner heater 36 that heats the bottom left side 34 and the left side sill 35, which are difficult to warm in the vehicle body 11, by applying radiant heat. The left side sill 35 is provided in the left pillar 33 and has a heat capacity larger than that of the left door outer panel 37 in the vehicle body 11 and is difficult to warm, so that radiant heat is applied and the temperature of the left side sill 35 becomes the temperature of the left door outer panel 37. A left outer heater 38 that heats up to approximate and a right column 39 that is provided on the right column 39 of the portal frame 32 and that heats the bottom right side 41 and the right side sill 42 that are difficult to warm in the vehicle body 11 by applying radiant heat. Radiant heat is applied to the inner heater 43 and the right side sill 42 which is provided on the right column 39 and has a heat capacity larger than that of the right door outer panel 44 and is difficult to warm. Temperature of the right side sill 42 and the right outer heater 45 for heating to approximate the temperature of the right door outer panel 44, made of Te.

The left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45 are each a near infrared lamp. The left inner heater 36 is provided with a left inner reflecting plate 47 surrounding the left inner filament 46. Since the light generated by the left inner filament 46 is collected by the left inner reflector 47, heat rays having directivity can be emitted to the vehicle body 11. Note that each of the left outer heater 38, the right inner heater 43, and the right outer heater 45 is also provided with a reflector surrounding the filament, like the left inner heater 36.

Also, the near-infrared lamp has a smaller specific heat capacity than the far-infrared lamp, so the response speed is fast. If the response speed is fast, quick output control can be performed in response to a command from the control unit. Since the waiting time until heating can be shortened, it contributes to shortening of the drying time.

In addition, the control unit 48 is provided in the drying furnace 20, and the control unit 48 controls the left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45. The control unit 48 sends an output command to the near-infrared lamp based on temperature information from the upstream temperature measurement unit (reference numeral 27 in FIG. 5) and the downstream temperature measurement unit (reference numeral 29 in FIG. 5). That is, the control unit 48 can control the output of the near infrared lamp. Next, the detailed structure of the upstream temperature measuring unit will be described with reference to FIG.

As shown in FIG. 7, the upstream temperature measuring unit 27 is provided on the left column 72 of the portal frame 71, and includes an upstream left first temperature measuring unit 73 that measures the temperature of the left side sill 35, and the left furnace wall. 74, an upstream left second temperature measuring unit 75 that measures the temperature of the left door outer panel 37, and a right upstream 76 that measures the temperature of the right side sill 42, provided on the right column 76 of the portal frame 71. A temperature measuring unit 77 and an upstream right second temperature measuring unit 79 that is provided on the right furnace wall 78 and measures the temperature of the right door outer panel 44.

The upstream left first temperature measuring section 73, the upstream left second temperature measuring section 75, the upstream right first temperature measuring section 77, and the upstream right second temperature measuring section 79 are non-contact sensors. These sensors detect thermal radiation emitted from the vehicle body 11 heated by hot air, and calculate the temperatures of the side sill and the door outer panel of the vehicle body 11.

In addition, the upstream left first temperature measuring unit 73, the upstream left second temperature measuring unit 75, the upstream right first temperature measuring unit 77, and the upstream right second temperature measuring unit 79 are connected to the control unit 48. ing. Based on the temperature information of the upstream left first temperature measuring unit 73 and the upstream left second temperature measuring unit 75, the control unit 48 uses the left inner heater (reference numeral 36 in FIG. 6) and the left outer heater (reference numeral in FIG. 6). The output command is issued to 38). For example, when the temperature of the left side sill 35 measured by the upstream left first temperature measuring unit 73 is lower than the temperature of the left door outer panel 37 measured by the upstream left second temperature measuring unit 75, the left A high output command is issued to the inner heater and the left outer heater.

In the upstream temperature measuring unit 27, the temperature of the left side sill 35 measured by the upstream left first temperature measuring unit 73 is greatly different from the temperature of the left door outer panel 37 measured by the upstream left second temperature measuring unit 75. In this case, a high output command is sent from the control unit 48 to the left inner heater (reference numeral 36 in FIG. 6) and the left outer heater (reference numeral 38 in FIG. 6). On the other hand, when the temperature of the left side sill 35 measured by the upstream left first temperature measuring unit 73 has a small difference from the temperature of the left door outer panel 37 measured by the upstream left second temperature measuring unit 75, A low output command is sent from the control unit 48 to the left inner heater and the left outer heater.

Thus, the temperature of the side sill of the vehicle body is compared with the temperature of the door outer panel, and the left inner heater and the left outer heater are controlled by the control unit 48 so as to output an appropriate amount of heat according to the temperature difference. Accordingly, an appropriate amount of heat can be applied to the side sill from the left inner heater and the left outer heater.

Moreover, the control part 48 is based on the temperature information of the upstream right 1st temperature measuring part 77 and the upstream right 2nd temperature measuring part 79, and a right inner side heater (code | symbol 43 of FIG. 6) and a right outer side heater (FIG. 6). The output command is also issued to the reference numeral 45). Next, the detailed structure of the downstream temperature measuring unit will be described with reference to FIG.

As shown in FIG. 8, the downstream temperature measuring unit 29 is provided on the left column 82 of the portal frame 81, and includes a downstream left first temperature measuring unit 83 that measures the temperature of the left side sill 35, and the left furnace wall. 74, a downstream left second temperature measuring unit 84 that measures the temperature of the left door outer panel 37, and a downstream right first that is provided on the right column 85 of the portal frame 81 and measures the temperature of the right side sill 42. The temperature measuring unit 86 includes a downstream right second temperature measuring unit 87 that is provided on the right furnace wall 78 and measures the temperature of the right door outer panel 44.

The downstream left first temperature measuring unit 83, the downstream left second temperature measuring unit 84, the downstream right first temperature measuring unit 86, and the downstream right second temperature measuring unit 87 are non-contact sensors. These sensors detect thermal radiation emitted from the vehicle body 11 heated by hot air, and calculate the temperatures of the side sill and the door outer panel of the vehicle body 11.

In addition, the downstream left first temperature measuring unit 83, the downstream left second temperature measuring unit 84, the downstream right first temperature measuring unit 86, and the downstream right second temperature measuring unit 87 are connected to the control unit 48. ing. Based on the temperature information of the downstream left first temperature measuring unit 83 and the downstream left second temperature measuring unit 84, the control unit 48 uses the left inner heater (reference numeral 36 in FIG. 6) and the left outer heater (reference numeral in FIG. 6). The output command is issued to 38). For example, when the temperature of the left side sill 35 measured by the downstream left first temperature measuring unit 83 is higher than the temperature of the left door outer panel 37 measured by the downstream left second temperature measuring unit 84, the left A low output command is issued to the inner heater and the left outer heater.

Moreover, the control part 48 is based on the temperature information of the downstream right 1st temperature measuring part 86 and the downstream right 2nd temperature measuring part 87, and a right inner side heater (code | symbol 43 of FIG. 6) and a right outer side heater (FIG. 6). The output command is also issued to the reference numeral 45).

The operation of the drying furnace described above will be described next.
As shown in FIG. 9 (a), the upstream left first temperature measuring section 73 measures the temperature of the left side sill 35 at the upstream temperature measuring section (reference numeral 27 in FIG. 7), and the upstream left second The temperature measuring unit 75 measures the temperature of the left door outer panel 37, the upstream right first temperature measuring unit 77 measures the temperature of the right side sill 42, and the upstream right second temperature measuring unit 79 measures the temperature of the right door outer panel 44. Measure.

The measurement result is that the temperature of the left side sill 35 is lower than the temperature of the left door outer panel 37, and the temperature of the right side sill 42 is lower than the temperature of the right door outer panel 44.

Based on the measurement result, the control unit 48 issues a high output command to the left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45 as shown in FIG. 9B. By this command, the left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45 irradiate the left side sill 35 and the right side sill 42 with near infrared rays in a concentrated manner. By irradiating the left side sill 35 and the right side sill 42, the temperature difference of the left side sill 35 with respect to the left door outer panel 37 and the temperature difference of the right side sill 42 with respect to the right door outer panel 44 can be eliminated. That is, each part of the vehicle body 11 can be heated uniformly.

In the drying furnace (reference numeral 20 in FIG. 4), the left side sill 35 and the right side sill 42 are moved by the left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45 in a state where the entire vehicle body 11 is heated with hot air. Heat locally. Radiant heat generated by the left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45 is absorbed by the left side sill 35 and the right side sill 42 in the form of electromagnetic waves. Can be reliably heated.

As shown in FIG. 3B, this heating raises the temperature of the side sill during the time Ta, so that the temperature of the side sill can be reliably approximated to the temperature of the door outer panel.

In FIG. 9B, if the left side sill 35 and the right side sill 42 are locally heated with hot air jetted from the jet nozzle in a state where the entire vehicle body 11 is heated with hot air, the jetted hot air is left left sill 35. And diffuse around the right side sill 42. Due to the diffusion of the hot air, the hot air does not reach the left side sill 35 and the right side sill 42, and the left side sill 35 and the right side sill 42 do not easily rise in temperature. In order to raise the temperature of the left side sill 35 and the right side sill 42, it is sufficient to continue heating. However, since the left door outer panel 37 and the right door outer panel 44 have already been heated, they receive extra heat.

In that regard, in the drying furnace of the embodiment (reference numeral 20 in FIG. 4), the left side sill 35 and the right side sill 42 in the vehicle body 11 are radiated by applying radiant heat so that the temperature of the left side sill 35 and the right side sill 42 is increased. And the temperature of the right door outer panel 44 can be reliably approximated. That is, since the left side sill 35 and the right side sill 42 and the left door outer panel 37 and the right door outer panel 44 can be heated substantially the same, extra heat is given to the left door outer panel 37 and the right door outer panel 44. There is no. Therefore, it is possible to provide a drying furnace capable of reducing the amount of extra heat given to the door outer panel.

In the embodiment, near infrared rays are used for local heating of the vehicle body 11. As shown in Table 1 above, far-infrared rays have an absorption rate of 74% in acrylic water-based paints, but they do not have any effect on the coating film applied to the inner surface of the vehicle body. On the other hand, near infrared rays have an absorption rate of 35% in iron. In the embodiment, by using near infrared rays as a heat source for local heating, iron, that is, the vehicle body is mainly heated, and the coating film on the inner surface is dried by the heat of the vehicle body.

Specifically, near-infrared rays are irradiated toward the outer coating 91 of the left side sill 35 as shown in FIG. When the irradiated near infrared rays are absorbed by the left side sill 35 as shown by the arrow (2), the left side sill 35 is heated. Since the heat of the left side sill 35 is transmitted to the inner surface 89 side of the left side sill 35, the inner coating film 92 of the left side sill 35 is dried. The inner surface 89 side of the left side sill 35 is a portion that is not directly irradiated with near infrared rays. That is, by using near infrared rays, the left side sill 35 can be heated without taking time by using the heat conduction of the left side sill 35 even for a portion that is not directly irradiated with near infrared rays.

Next, the drying method implemented using a drying furnace is demonstrated.
As shown in FIG. 10, in step (hereinafter referred to as ST) 01, the temperature of the material to be dried is increased. Specifically, as shown in FIG. 4, the temperature of the vehicle body 11 is raised by the first hot air heating unit 23.

In ST02, the temperature of a part of the material to be dried that has a heat capacity larger than that of the other part and is difficult to warm is measured by the first temperature measuring unit, and the temperature of the other part is measured by the second temperature measuring unit. Specifically, as shown in FIG. 9A, the upstream side temperature measuring unit 27 measures the temperature of the left side sill 35 by the upstream left first temperature measuring unit 73, and the upstream left second temperature measuring unit. The temperature of the left door outer panel 37 is measured by the section 75, the temperature of the right side sill 42 is measured by the upstream right first temperature measuring section 77, and the temperature of the right door outer panel 44 is measured by the upstream right second temperature measuring section 79. To do.

In ST03, radiant heat is applied to a portion that is difficult to warm in the object to be dried so that the temperature of the portion that is difficult to warm is approximated to the temperature of the other portion. Specifically, as shown in FIG. 9B, the left inner heater 36, the left outer heater 38, the right inner heater 43, and the right outer heater 45 concentrate near infrared rays on the left side sill 35 and the right side sill 42. Irradiate.

In ST04, the temperature of the material to be dried is kept constant. Specifically, as shown in FIG. 4, the temperature of the vehicle body 11 whose temperature has been raised is held by the second hot air heating unit 24.

The drying method is performed using a drying furnace 20 that dries the vehicle body 11 with hot air. Further, the drying method includes a temperature raising step for raising the temperature of the vehicle body 11, and the temperature of the left side sill 35 is measured by the upstream left first temperature measuring unit 73 in FIG. The temperature measurement step of measuring the temperature of the left door outer panel 37 by the unit 75, and in FIG. 9B, radiant heat is applied to the left side sill 35 so that the temperature of the left side sill 35 approximates the temperature of the left door outer panel 37. It consists of a local heating step for heating and a temperature holding step for keeping the temperature of the vehicle body 11 constant in FIG.

9B, the radiant heat used in the local heating process is absorbed by the vehicle body 11 in the form of electromagnetic waves, so that the left side sill 35 can be reliably heated. In FIG. 3, since the side sill is heated by locally heating the side sill during time Ta, the temperature of the side sill can be reliably approximated to the temperature of the door outer panel.

In FIG. 9B, if the left side sill 35 is locally heated with hot air jetted from the jet nozzle while the vehicle body 11 is entirely heated with hot air, the jetted hot air diffuses around the left side sill 35. To do. Due to the diffusion of the hot air, the hot air does not reach the left side sill 35, and the temperature of the left side sill 35 is difficult to increase. In order to raise the temperature of the left side sill 35, it is only necessary to continue heating. However, since the left door outer panel 37 has already been heated, excess heat is received.

In that respect, in the drying method of the present invention, the temperature of the left side sill 35 can be reliably approximated to the temperature of the left door outer panel 37 by applying radiant heat to the left side sill 35 in the local heating step. That is, since the temperature of the side sill and the door outer panel can be raised substantially the same, extra heat is not applied to the door outer panel. Therefore, it is possible to provide a drying method that can reduce the amount of extra heat given to the door outer panel.

In addition, the vehicle body 11 is a thing that has been painted before entering the drying furnace (reference numeral 20 in FIG. 4). In the local heating process, the time point at which radiant heat is applied to the side sill in FIG. This is the time when the temperature of the side sill measured by the first temperature measuring unit reaches the crosslinking temperature of the paint applied to the vehicle body.

If the painted vehicle body is placed in a drying furnace and radiant heat is applied to the side sill of the vehicle simultaneously with the start of hot air drying as shown in FIG. 2 (a), the paint applied to the side sill is fluidized. . However, by locally heating the side sill with radiant heat, the rate of temperature rise of the side sill increases, so that the paint becomes hot and the paint hardens while the flow is insufficient. Therefore, it becomes difficult for the coating film to become smooth, and the quality of the coating film decreases.

In that respect, in the drying method of the embodiment, when the temperature of the side sill of the vehicle body reaches the crosslinking temperature of the paint applied to the side sill as shown in FIG. 2B, radiant heat is applied to the side sill. That is, local heating by radiant heat is performed on the side sill when a certain time has elapsed from the start of hot air drying. Between the start of hot air drying and the start of local heating, the paint applied to the side sill is fluidized. Since the temperature rise rate of the side sill is small at the start of hot air drying, the paint flows sufficiently and then becomes hot and solidifies. Therefore, since a smooth coating film can be obtained, the quality of the coating film is improved.

Furthermore, in the embodiment, since near infrared rays are used as a heat source for radiant heat, iron, that is, the vehicle body is mainly heated, and the coating on the inner surface can be dried by the heat of the vehicle body.

In addition, although the Example illustrated the vehicle body by which the coating was given as a to-be-dried object, this invention is applicable also to the machine and structure already coated.
Further, in the above description, the side sill of the vehicle body is exemplified as “a part having a larger heat capacity than other parts and is not easily warmed”, but “a part having a larger heat capacity and less likely to be warmed than other parts” Part.
Furthermore, in the above description, the door outer panel is exemplified as the “other part”, but the “other part” may be a thin body portion of the vehicle body such as a hood outer panel or a lid outer panel.

DESCRIPTION OF SYMBOLS 11 ... To-be-dried object (vehicle body), 20 ... Drying furnace, 35 ... The part which is hard to warm (left side sill), 36 ... Heater (left inner heater), 37 ... Other parts (left door outer panel), 38 ... Heater (left outer) Heater), 42 ... Parts that are difficult to warm (right side sill), 43 ... Heater (right inner heater), 44 ... Other parts (right door outer panel), 45 ... Heater (right outer heater), 48 ... Control unit, 73 ... 1 temperature measuring section (upstream left first temperature measuring section), 75 ... second temperature measuring section (upstream left second temperature measuring section), 77 ... first temperature measuring section (upstream right first temperature measuring section) 79 ... second temperature measuring section (upstream right second temperature measuring section)

Claims

A drying furnace (20) for drying an object to be dried (11) with hot air,
In the object to be dried (11), the temperature of the part (35, 42) which is difficult to warm by applying radiant heat to the part (35, 42) which has a larger heat capacity than the other part (37, 44) and is difficult to warm. Heaters (36, 38, 43, 45) for heating to approximate the temperature of the other parts (37, 44),
A drying furnace.
The drying furnace according to claim 1, wherein the heater (36, 38, 43, 45) is a near infrared lamp.
A first temperature measuring section (73, 77) that is provided upstream of the heater (36, 38, 43, 45) and measures the temperature of the portion (35, 42) that is difficult to warm, and the other portion (37 , 44) a second temperature measuring section (75, 79) for measuring the temperature of
A control unit (48) for controlling the output of the heater (36, 38, 43, 45) based on temperature information of the first temperature measuring unit (73, 77) and the second temperature measuring unit (75, 79). )When,
The drying furnace according to claim 1, further comprising:
A drying method for drying an object to be dried (11) with hot air using a drying furnace (20),
A temperature raising step for raising the temperature of the object to be dried (11);
In the object to be dried, the temperature of the part (35, 42) having a heat capacity larger than that of the other part (37, 44) and difficult to warm is measured by the first temperature measuring unit (73, 77), and the other part ( 37, 44) a temperature measuring step of measuring the temperature of the second temperature measuring section (75, 79);
Radiation heat is applied to the part (35, 42) that is difficult to warm in the object to be dried so that the temperature of the part (35, 42) that is difficult to warm approximates the temperature of the other part (37, 44). A local heating process,
A temperature holding step for keeping the temperature of the object to be dried (11) constant;
A drying method comprising:
The to-be-dried object (11) is an object that has been coated before being put into the drying furnace (20),
In the local heating step, when the radiant heat is applied to the part (35, 42) that is difficult to warm in the dried object, the part (35, 42) that is difficult to warm measured by the first temperature measuring part (73, 77). Is the time when the temperature reaches the crosslinking temperature of the paint applied to the material to be dried,
The drying method according to claim 4.
The drying method according to claim 4 or 5, wherein the heat source of the radiant heat is near infrared rays.